All I ask is a chance to prove that money can't
make me happy.

Concept 7.4 : Moving Light Source With Viewpoint
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To create a light that moves along with the viewpoint
you need to set the light position before the viewing
transformation.  then the viewing transformation 
affects both the light and the viewpoint in the same
way.  

Here in the initial condition we see the front of 
the cube.  By clicking anywhere on the screen you 
should see the image toggle and show the front and
back faces of the cube repeatedly.
Notice how the lighting is consistent regardless of
whether we see the front or the back of the cube.
Compare this to Concept 7.2 where the light
was stationary and the back side appeared to be 
shrouded in darkness.


Everytime the cube is redrawn both the viewpoint and
the light source see a change of location!!.